Field of the Invention
The present invention relates to a scintillator, a method of manufacturing the same, a radiation imaging apparatus, and a radiation imaging system.
Description of the Related Art
A scintillator can be manufactured by, for example, growing a plurality of columnar crystals on a base. In manufacturing the scintillator, columnar crystals may grow abnormally. A portion formed by abnormal growth can be referred to as, for example, an abnormally grown portion. The abnormally grown portion becomes higher than another portion and constitutes a portion that protrudes more than the other portion on the surface of a scintillator layer. Therefore, when the scintillator including the abnormally grown portion is bonded to a sensor array in which a plurality of sensors (photoelectric conversion portions) are arrayed, a considerable interspace needs to be provided between the scintillator and the sensor array. However, such an arrangement can be a cause of decreasing Detective Quantum Efficiency (DQE) and Modulation Transfer Function (MTF).
Japanese Patent No. 4800434 describes a method of forming a columnar crystal of CsI as a scintillator by vapor deposition, and then placing a glass plate on the surface of CsI including an abnormally grown portion and applying 1 atmospheric pressure to CsI in order to planarize the surface. Japanese Patent Laid Open No. 2010-25620 does not mention abnormal growth. However, this literature describes a method of forming a plurality of fluorescent columnar crystals, and then covering the front end portions thereof with a material having a refractive index lower than that of each crystal and polishing a layer made of the plurality of fluorescent columnar crystals and the material having the lower refractive index. Executing the method described in Japanese Patent Laid Open No. 2010-25620, it is understood that an abnormally grown portion can be polished if it exists.
In the method described in Japanese Patent No. 4800434, the scintillator may be damaged by applying the pressure to the abnormally grown portion and a portion other than this. Therefore, it can be difficult to increase a yield rate, increasing a manufacturing cost. In the method described in patent Japanese Patent Laid Open No. 2010-25620, all the fluorescent columnar crystals can be exposed by polishing, and thus deteriorated by water. That is, it may be difficult to obtain a high-quality scintillator at a low cost with the methods described in Japanese Patent No. 4800434 and Japanese Patent Laid Open No. 2010-25620.